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1.
Polymers (Basel) ; 15(22)2023 Nov 07.
Artículo en Inglés | MEDLINE | ID: mdl-38006068

RESUMEN

The fabrication of PVDF-based nanofiber mats with enhanced ß-phase using electrospinning and post processing was optimized using Taguchi design methodology. The parameters studied include the concentration of PVDF in the DMF (Dimethylformamide) solvent, applied voltage, flow rate, and drum speed. A reliable statistical model was obtained for the fabrication of bead-free PVDF nanofibers with a high fraction of ß-phase (F(ß)%). The validity of this model was verified through comprehensive regression analysis. The optimized electrospinning parameters were determined to be a 23 wt% PVDF solution, 20 kV voltage, a flow rate of 1 mL/h, and a drum speed of 1200 revolutions per minute.

2.
J Biomater Appl ; 38(4): 484-499, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37807545

RESUMEN

In this study, 3D printing of poly-l-lactic acid (PLLA) scaffolds reinforced with graphene oxide (GO) nanoparticles via Digital Light Processing (DLP) was investigated to mimic bone tissue. Stereolithography is one of the most accurate additive manufacturing methods, but the dominant available materials used in this method are toxic. In this research, a biocompatible resin (PLLA) was synthetized and functionalized to serve the purpose. Due to the low mechanical properties of the printed product with the neat resin, graphene oxide nanoparticles in three levels (0.5, 1, and 1.5 wt%) were added with the aim of enhancing the mechanical properties. At first, the optimum post cure time of the neat resin was investigated. Consequently, all the parts were post-cured for 3 h after printing. Due to the temperature-dependent structure of GO, all samples were placed in an oven at 85°C for different time periods of 0, 6, 12, and 18 h to increase mechanical properties. The compression test of heat-treated samples reveals that the compressive strength of the printed parts containing 0.5,1, and 1.5% of GO increased by 151,162 ad 235%, respectively. Scaffolds with the designed pore sizes of 750 microns and a porosity of 40% were printed. Surface hydrophilicity test was performed for all samples showing that the hydrophilicity of the samples increased with increasing GO percentage. The degradation behavior of the samples was evaluated in a PBS environment, and it revealed that by increasing GO, the rate of component degradation increased, but the heat treatment had the opposite effect and decreased the degradation rate. Finally, besides improving biological properties, a significant increase in mechanical properties under compression can introduce the printed scaffolds as a suitable option for bone implants.


Asunto(s)
Grafito , Andamios del Tejido , Andamios del Tejido/química , Poliésteres , Grafito/química , Impresión Tridimensional
3.
Polymers (Basel) ; 15(14)2023 Jul 18.
Artículo en Inglés | MEDLINE | ID: mdl-37514466

RESUMEN

In this research, polypropylene (PP)-graphite composites were prepared using the melt mixing technique in a twin-screw extruder. Graphite, multi-walled carbon nanotubes (MWCNT), carbon black (CB), and expanded graphite (EG) were added to the PP in binary, ternary, and quaternary formations. The graphite was used as a primary filler, and MWCNT, CB, and EG were added to the PP-graphite composites as secondary fillers at different compositions. The secondary filler compositions were considered the control input factors of the optimization study. A full factorial design of the L-27 Orthogonal Array (OA) was used as a Design of Experiment (DOE). The through-plane electrical conductivity and flexural strength were considered the output responses. The experimental data were interpreted via Analysis of Variance (ANOVA) to evaluate the significance of each secondary filler. Furthermore, statistical modeling was performed using response surface methodology (RSM) to predict the properties of the composites as a function of filler composition. The empirical model for the filler formulation demonstrated an average accuracy of 83.9% and 93.4% for predicting the values of electrical conductivity and flexural strength, respectively. This comprehensive experimental study offers potential guidelines for producing electrically conductive thermoplastic composites for the manufacturing of bipolar fuel cell plates.

4.
J Mech Behav Biomed Mater ; 112: 104064, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-32911225

RESUMEN

The main aim of this paper is to assess the impacts of design, porosity, and biodegradation on the mechanical and morphological properties of triply periodic minimal surface (TPMS) scaffolds. The TPMS scaffolds were designed and manufactured with different porosities by using fused deposing modeling (FDM) technique. The biodegradation test on the scaffolds was performed for four and six months. The mechanical properties were assessed employing ASTM standard compression test and an in-situ mechanical testing stage. Microcomputed tomography (Micro-CT) technique was used to investigate detailed morphological properties of the scaffolds in 3D. Results indicate that the Schwarz-D scaffolds exhibit the highest compressive strength in lower porosity scaffolds but lose mechanical properties when the porosity was increased. On the contrary, Gyroid scaffolds maintain their strength as the porosity was increased. In addition, Gyroid scaffolds preserve a higher percentage of their compressive strength after six months of biodegradation. It was also observed that biodegradation phenomenon transformed the mechanical failure mode of the scaffolds from ductile to brittle. Morphological analysis of the scaffolds revealed detailed information, which support and clarify the observed variations in the mechanical properties.


Asunto(s)
Huesos , Andamios del Tejido , Fuerza Compresiva , Porosidad , Propiedades de Superficie , Ingeniería de Tejidos , Microtomografía por Rayos X
5.
Sci Total Environ ; 664: 363-373, 2019 May 10.
Artículo en Inglés | MEDLINE | ID: mdl-30743128

RESUMEN

Bamboo-derived biocarbon (BA900) and wood-derived biocarbon (THOC700) have exhibited graphite-like characteristics through transmission electron microscopy, X-ray diffraction (XRD), and Attenuated Total Reflectance (ATR) spectroscopy analysis. Lightweight composites of biocarbons were manufactured by a mechanism of shear controlled melt-phase mixing, ensuring the preservation of biocarbon pore structures and simultaneously taking full advantage of low density polyolefin substrates. Effective tensile strength was improved by approximately 10% in the polypropylene-based bamboo carbon composite, whereas no appreciable improvement was observed in the tensile and impact strength of bamboo-derived biocarbon formulations compared to neat polymer. However, the tensile and flexural moduli and flexural strength of the THOC700-PP composites were significantly enhanced, by 56%, 67%, and 19%, respectively, compared to neat polymer. The most significant finding of the investigation was the retention of density in polyolefin polymer (ρPP = 0.91; ρTHOC = 0.95; ρBA900 = 0.99), with enhanced mechanical performance useful for lightweighting applications. Bamboo biocarbon provides a viable alternative to another abundantly available industrial carbon feedstock, reclaimed carbon fiber (RCF), in manufacturing thermoplastic composites. The origin of the carbon plays an important role in defining ultimate composite performance. A mechanism for retaining lightweight structural performance has been proposed in this original work, paving the way to develop next-generation lightweight thermoplastic structures for transportation and other industrial and consumer products.


Asunto(s)
Fibra de Carbono , Materiales de Construcción , Carbono , Grafito , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Polímeros , Polipropilenos , Porosidad , Resistencia a la Tracción , Madera , Difracción de Rayos X
6.
J Mech Behav Biomed Mater ; 91: 266-277, 2019 03.
Artículo en Inglés | MEDLINE | ID: mdl-30605857

RESUMEN

In this study the effects of foaming process on the shape memory properties of Polylactic acid/thermoplastic polyurethane/cellulous-nanofiber bio-nanocomposites were investigated. The samples of cylindrical shapes as well as sheets were manufactured and foamed. The results indicated that while the foaming process presented a microcellular structure, it can cause a tangible increase (up to 40%) in force recovery ratio and an intense reduction (up to 10 times) in actuation force. It is statistically shown that the existence of cellulose nano-fibers within the foamed matrix causes a significant increase in actuation force and reduction in the force recovery ratio. Analytical evaluation on the sheet form samples, in the foamed state using rheological model, was carried out that indicated satisfying description of their shape memory behaviors. It was also demonstrated that there exists significant deviation between the shape memory properties extracted from experimental and analytical assessments.


Asunto(s)
Celulosa/química , Fenómenos Mecánicos , Nanocompuestos/química , Poliésteres/química , Poliuretanos/química , Temperatura , Ensayo de Materiales , Reología
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